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Cycling is the most important phase of a newly setup aquarium. This process establishes the beneficial bacteria in the aquarium to convert the toxic wastes, uneaten food etc. into Nitrate with the help of beneficial bacteria.  This bacteria is called Nitrifying bacteria and process is known as biological or nitrogen cycle. Sometimes this cycle turns into a disaster for the aquarist without proper knowledge.
This bacteria establishes colonies in the aquarium, filter and filter media to convert Ammonia into Nitrite and Nitrite into Nitrate.  This process can take two week to two months to complete. During this period the aquarium shows different symptoms like as diatoms, algae, bacteria bloom, infection and death of fishes.

How to determine the completion of Cycling?

Keep your eyes on the water parameters of aquarium. During the first 6 to 10 days the Ammonia level rises. After two weeks or so on the Nitrite level rises and Ammonia level decreases. After few more days, the Nitrate level increases and Nitrite level decreases. The dropping of Nitrite level indicates that the cycling period is almost complete. When water do not show the presence of Ammonia and Nitrite, it means the aquarium has been crossed the most important hurdle and ready to introduce fishes. But it is still not ready to house the sensitive fishes.

How to start the Cycling?

There are two ways to start the cycling of tank i.e. Fishless Cycling or with fish.

  1. Fishless Cycling: Ammonia and Nitrite both are the killer for the fishes. Although some hardy fishes like as mollies, guppies, barbs are able to tolerate but it is not a good idea to introduce fishes in a newly setup aquarium during the cycling period. This can cause fish to become stressed or infected with several diseases. Even it can easily kill the precious life of fishes. But the newly setup aquarium owners do not know the fact and soon their aquarium turns into a cemetery ground for fishes.
    Their money goes into pocket of shopkeeper and fishes lost their lives. So it is best idea to start aquarium with a few hardy fishes or without fishes. To start a fishless cycle, there are some options. Some of these are following:

Option 1: I prefer to install a filter/filter media/ mulm from a cycled tank. This will seed the aquarium with beneficial bacteria and presence of Nitrate will be appearing within 3-4 days or a week. This is the fastest mode to cycle a tank. But used filter or filter media can also introduce snails, planeria or some other invertebrates in the newly setup tank. So check everything seriously.

Option 2: Daily drop some fish food/ raw meat/fish/shrimp in the aquarium for a few days. This food will decompose and produce Ammonia into the aquarium to start the cycling.

Option 3: There are some commercial products available in the market to reduce the cycling period by establishing beneficial bacteria colonies into the aquarium. Use these products to reduce the cycling period.

Option 4: Ammonium hydroxide (NH4OH) or Ammonium chloride (NH4Cl) can also be use to release Ammonia into the aquarium. Ammonium hydroxide is also known as Ammonia solution and it is easily available in the market. It is a colorless aqueous solution. Ammonia vapors (arise from the solution) irritates the eyes. So use it with caution. Mix 1 drop of Ammonia solution in eight liter of water until the Nitrate reading appears. Repeat the dosing till the Nitrate level rises into the aquarium.

  1. Cycling with Fish: Cycling a newly setup aquarium can be nightmare for fishes/invertebrates due to presence of excess Ammonia/Nitrates. Livestock can be easily get stressed and infected to diseases. Ammonia is an essential ingredient to start the cycling process. Decomposing fish waste and uneaten food adds Ammonia in aquarium. Adding fish in a newly setup aquarium don’t require external source of Ammonia.

Never add too many fishes in the new aquarium during cycling period. Only two small fishes in 40 liter tank are enough. More fishes will produce more waste and result can be Ammonia spike. In the early days, the beneficial bacteria will be in limited quantity and unable to consume too much Ammonia of a overstocked aquarium.

Cycling is also called new tank syndrome due to the overcome of many problems during the period.

Phases of Nitrogen Cycle

The cycling period can divide into three phases.

Phase 1: Ammonia is produced in the aquarium using Fish waste/meat or other methods. Fish waste/food decomposes and produces Ammonia. It can be either Ammonium (NH4) or Ammonia (NH3). Production of Ammonium or Ammonia depends on the pH of water. If pH is less than 7, Ammonium will be produced while the pH above 7.5 produce Ammonia. Keep in mind that Ammonium is not harmful for the health of fishes.

Phase 2: After few days of aquarium setup, the bacteria Nitrosomones get develop. These bacteria consume Ammonia and produce Nitrite as byproduct. Nitrite is also very toxic and harmful. Frequent water change keeps Nitrite under control.

Phase 3: In next stage, cycling started with the development of another bacteria Nitrobacter which is responsible to convert the Nitrite into Nitrates. Nitrate is also harmful for the lives in the aquarium. But it can be easily reduce by time to time water change. Appearance of Nitrate indicates end of cycling period.

How to speed up the Cycling

A suitable condition in the aquarium helps in completing cycling period speedily.

Cycling aquarium need patience. The aquarist should not be annoyed or irritate, during cycling period. Success of an aquarium depends on cycling process. Always keep an eye on water parameters. Frequent water change is the key of success.